1. Field of the Invention
The present invention relates to a three-level inverter in which one phase of an output thereof is grounded, a power conditioner, and a power generating system.
2. Discussion of the Background
Japanese Unexamined Patent Application Publication No. 2002-176784 discloses a neutral voltage controller included in a three-level inverter. The neutral voltage controller described in this document controls a voltage (neutral voltage) between a connecting point (neutral point) of two capacitors connected in series between a positive bus and a negative bus of the three-level inverter and the negative bus. When the neutral voltage varies, a direct-current component is superimposed on an output current.
In the three-level inverter including the neutral voltage controller described in this document, none of the U-phase, V-phase, and W-phase is grounded. The three-level inverter has three arms, a U-phase arm, a V-phase arm, and a W-phase arm, each of which outputs a voltage of each phase. Therefore, a calculator included in this three-level inverter is capable of directly generating a neutral-voltage control command in a fixed coordinate system, controlling an arm that outputs a neutral voltage on the basis of the generated neutral-voltage control command, and suppressing variations in neutral voltage.